1. Field of Invention
The present invention relates to a structure of an exhaust pipe for exhaust heat recovery, and more particularly to a structure of an exhaust pipe for exhaust heat recovery, which can more rapidly increase a temperature of coolant by increasing an area where heat exchange is performed between exhaust heat of exhaust gas and heat of a cold coolant, and arranging a flow direction of the coolant to be opposite to a flow direction of the exhaust gas.
2. Description of Related Art
In order to allow an engine of a vehicle exposed to a cold air temperature in a winter season to normally operate and to increase combustion efficiency of fuel, warming-up is required prior to driving or during an initial driving period.
An exhaust heat recovery apparatus is an apparatus which rapidly heats cold coolant with waste exhaust heat during an initial driving period in a winter season. The exhaust heat recovery apparatus has been developed to improve fuel efficiency by reducing friction loss inside the engine by shortening the warming-up time of the engine.
The exhaust heat recovery apparatus in the related art is shown in FIG. 1. Referring to FIG. 1, a housing 2 in a barrel shape having an enlarged diameter is mounted at a predetermined position of an exhaust pipe 1 through which exhaust gas generated in the engine flows.
In addition, an inlet and an outlet, through which the coolant (circulating in the engine and a radiator) flows in and flows out, are respectively formed in the housing 2, and heat transfer plates 3 are arranged inside the housing 2 to form channels through which the coolant flows. Further, a bypass valve 4 is coupled to the exhaust pipe positioned inside the housing 2 so as to open and close the exhaust pipe 1 (based on electrical signals), and a hole 4a is formed in a surface of the exhaust pipe inside the housing 2. Therefore, when the bypass valve 4 is closed, a path (depicted by an arrow) is formed so that the exhaust gas can flow into a space where the heat transfer plates 3 are positioned from the inside of the housing 2.
Therefore, when the engine is at a normal temperature, the bypass valve 4 is opened so that a large amount of the exhaust gas flows (toward the outlet) without being in contact with the heat transfer plates 3. Further, when the engine is at a low temperature, the bypass valve 4 is closed so that the coolant circulates inside the housing 2 so as to be heated.
However, in the related art, an area where the heat exchange is performed is limited because the heat transfer plate 3 has a simple pipe shape, and flow resistance is caused because flow paths of the exhaust gas are not simple.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.